A week before she was killed by a suicide bomber, humanitarian worker Marla Ruzicka forced military commanders to admit they did keep records of Iraqi civilians killed by US forces.

Tommy Franks, the former head of US Central Command, famously said the US army "don't do body counts", despite a requirement to do so by the Geneva Conventions.

But in an essay Ms Ruzicka wrote a week before her death on Saturday and published yesterday, the 28-year-old revealed that a Brigadier General told her it was "standard operating procedure" for US troops to file a report when they shoot a non-combatant.

She obtained figures for the number of civilians killed in Baghdad between 28 February and 5 April, and discovered that 29 had been killed in firefights involving US forces and insurgents. This was four times the number of Iraqi police killed.

"These statistics demonstrate that the US military can and does track civilian casualties," she wrote. "Troops on the ground keep these records because they recognise they have a responsibility to review each action taken and that it is in their interest to minimise mistakes, especially since winning the hearts and minds of Iraqis is a key component of their strategy."

Sam Zia-Zarifi, deputy director of the Asia division of Human Rights Watch, the group for which Ms Ruzicka wrote the report, said her discovery "was very important because it allows the victims to start demanding compensation". He added: "At a policy level they have never admitted they keep these figures."

Exactly how many Iraqi civilians have been killed in the last two years is unclear. Iraq Body Count, a group that monitors casualty reports, says at least 17,384 have died. But the group bases its totals only on deaths reported by the media, and says it can therefore only "be a sample" of the total actually killed. Its website says: "It is likely that many if not most civilian casualties will go unreported by the media. That is the sad nature of war."

A peer-reviewed report published last year in The Lancet and based on an extrapolation of data suggested that 100,000 civilians may have been killed during the invasion and its aftermath. One of the report's author, Dr Richard Garfield, professor of nursing at Columbia University, said: "Of course they keep records and of course they pretend they don't. Why is it important to keep the numbers of those killed? Well, why was it important to record the names of those people killed in the World Trade Centre? It would have been inconceivable not to. These people have lives of value.

"We are still fighting [to record] the Armenian genocide. Until people have names and are counted they don't exist in a policy sense."

Ms Ruzicka, from California, was killed in Baghdad after her car was caught in the blast of a suicide bomber who attacked a convoy of security contractors on the road to the city's airport. She was in Iraq heading, Civic, the organisation she set up to record and document civilians killed or injured by the US military, and to seek compensation. She carried out a similar project in Afghanistan.

In her report, she wrote from Iraq: "In my dealings with the US military officials here, they have shown regret and remorse for the deaths and injuries of civilians. Systematically recording and publicly releasing civilian casualty numbers would assist in helping the victims who survive to piece their lives back together."

Colleagues of Ms Ruzicka at Civic (Campaign for Innocent Victims In Conflict) have vowed to continue her work. April Pedersen, a friend, said: "We are all committed to ensuring the work that Marla did is going to continue." Ms Ruzicka, whose funeral service is to be in California on Saturday, was also remembered on Capitol Hill where Senator Patrick Leahy, with whom Ms Ruzicka worked to achieve almost $20m in appropriations to help victims in Afghanistan and Iraq, paid tribute to her.

He said: "I want to... pay tribute to a remarkable young woman from Lakeport, California. In my 31 years as a United States Senator I have met lots of interesting and accomplished people from all over the world. We all have. Nobel prize winners, heads of state, people who have achieved remarkable and even heroic things in their lives. I have never met anyone like Marla Ruzicka." Meanwhile the Pentagon maintained its position that it did not keep numbers of civilians killed in Iraq.

'The public must know how many have died'

This is an edited extract of an article written by Marla Ruzicka a week before her death:

In my two years in Iraq, the one question I am asked the most is: "How many Iraqi civilians have been killed by American forces?" The American public has a right to know how many Iraqis have lost their lives since the start of the war and as hostilities continue.

In a news conference at Bagram air base in Afghanistan in March 2002, General Tommy Franks said: "We don't do body counts." His words outraged the Arab world.

During the Iraq war, as US troops pushed toward Baghdad, counting civilian casualties was not a priority for the military. Since 1 May 2003, when President Bush declared major combat operations over and the US military moved into "stability operations", most units began to keep track of civilians killed at checkpoints or during patrols by US soldiers.

Here in Baghdad, a brigadier general explained to me that it is standard procedure for US troops to file a spot report when they shoot a non-combatant. It is in the military's interest to release these statistics.

A number is important not only to quantify the cost of war, but as a reminder of those whose dreams will never be realised in a free and democratic Iraq.